Introduction to Retaining Walls

1. RETAINING WALLS

2. RETAINING WALL
 Basic function – to
retain soil at a slope
which is greater than
it would naturally
assume, usually at a
vertical or near
vertical position

4.  Retaining wall failure at the Shin-Kang Dam

5. Design of retaining wall
 retaining walls have primary function of
retaining soils at an angle in excess of the
soil’s nature angle of repose.
 Walls within the design height range are
designed to provide the necessary resistance
by either their own mass or by the principles
of leverage.
 Design consideration:
1. Overturning of the wall does not occur
2. Forward sliding does not occur
3. Materials used are suitable
4. The subsoil is not overloaded

6. Factors which designer need to take
account
 Nature and characteristics of the subsoil's
 Height of water table – the presence of water
can create hydrostatic pressure, affect bearing
capacity of the subsoil together with its shear
strength, reduce the frictional resistance
between the underside of the foundation
 Type of wall
 Materials to be used in the construction

8.  Failure of retaining wall (dam) due to water
pressure..

9. Types of walls
• Mass retaining walls
• Cantilever walls
• Counterfort retaining
walls
• Precast concrete
retaining walls
• Precast concrete crib-
retaining walls

10. Mass retaining walls
 Sometimes called gravity walls and rely upon
their own mass together with the friction on the
underside of the base to overcome the
tendency to slide or overturn
 Generally only economic up to 1.8 m
 Mass walls can be constructed of semi-
engineering quality bricks bedded in a 1:3
cement mortar or of mass concrete
 Natural stone is suitable for small walls up to
1m high but generally it is used as a facing
material for walls over 1 m

11. Typical example of mass retaining
walls
BRICK MASS RETAINING WALL

12. Brick retaining
wall
Stone retaining wall

13. Typical example of mass retaining
walls
MASS CONCRETE RETAINING WALL
WITH STONE FACINGS

14. Cantilever walls
 Usually of reinforced concrete and work on the
principle of leverage where the stem is
designed as a cantilever fixed at the base and
the base is designed as a cantilever fixed at the
stem
 Economic height range of 1.2 m to 6 m using
pre-stressing techniques
 Any durable facing material can be applied to
the surface to improve appearance of the wall

15. Cantilever wall

16.  Two basic forms:-
• A base with a large heel
• A cantilever with a large toe
Cantilever T Cantilever L

18. Cantilever walls

21. Counterfort retaining walls
 Can be constructed of reinforced or prestressed
concrete
 Suitable for over 4.5 m
 Triangular beams placed at suitable centres
behind the stem and above the base to enable
the stem and base to act as slab spanning
horizontally over or under the counterforts

25. Precast concrete retaining wall
 Manufactured from high-grade pre cast concrete on the
cantilever principle.
 Can be erected on a foundation as permanent retaining
wall or be free standing to act as dividing wall between
heaped materials which it can increase three times the
storage volume for any given area
 Other advantages- reduction in time by eliminating
curing period, cost of formwork, time to erect and
dismantle the temporary forms
 Lifting holes are provided which can be utilized for
fixing if required

26. application

28. Precast concrete retaining walls

29. Pre cast concrete crib-retaining walls
 Designed on the principle of mass retaining
walls
 A system of pre cast concrete or treated timber
components comprising headers and stretchers
which interlock to form a 3 dimensional
framework or crib of pre cast concrete timber
units within which soil is retained
 Constructed with a face batter between 1:6 and
1:8
 Subsoil drainage is not required since the open
face provides adequate drainage.